Fuse having a sand core



Feb. 6, 1968 c. MOCLURE, JR 3,368,047

FUSE HAVING A SAND coma Filed June 19, 1967 INVENTOR Charles McClure,Jr.

ATTORNEY United States Patent 3,368,047 FUSE HAVING A SAND CORE CharlesMcClure, Jr., Mercer, Pa., assignor to Westinghouse ElectricCorporation, Pittsburgh, Pa., a corporation of PennsylvaniaContinuation-impart of application Ser. No. 435,423,

Feb. 26, 1965. This application June 19, 1967, Ser.

Claims. (Cl. 200120) ABSTRACT OF THE DISCLQSURE This application is acontinuation-in-part of copending application Ser. No. 435,423, filedFeb. 26, 1965, now abandoned.

Description of the prior art It is old in the art to make a currentlimiting fuse by Winding a series of turns of a silver fuse element on acenter mandrel or core composed of ceramic or other suitable material,and placing the core and fuse element in a tube which is filled with aspecial sand. The sand provides an arc quenching action, and alsoprovides some space for temporarily storing the gas produced by the arc.

I have discovered that improved performance can be obtained by alsomaking the center mandrel or core of sand, so that the mandrel or corealso contributes to the space available for gas storage.

Summary of the invention According to one embodiment of my invention, Imake the mandrel out of sand by pressing it in a mold with a suitablebinder and then baking it to eliminate volatile material. The shape ofthe core or mandrel is cylindrical or ribbed or spiral as desired,according to different embodiments of the invention.

Accordingly, a primary object of my invention is to provide a new andimproved fuse offering advantages over any now existing in the art.

Another object is to provide a new and improved fuse having a sand core.

A further object is to provide a new and improved core for a fusecomposed of bound sand and rigid enough to wind a fuse element upon, butwhich will be blown apart, freeing the sand therein, by the energy ofthe are when the fuse blows.

These and other objects will become more fully apparent after a study ofthe following specification, when read in connection with theaccompanying drawings, in which:

Brief description of the drawings FIGURE 1 is a view partially incross-section of a fuse constructed according to one embodiment of myinvention;

FIG. 2 is a view of the core and fuse element of FIG. 1, showing thecore and fuse element in greater detail;

FIG. 3 is a view showing a core and fuse element according to a secondembodiment of my invention; and

FIG. 4 is a view showing a core and fuse element according to a thirdembodiment of my invention.

3,368,47 Patented Feb. 6, 1968 Description of the preferred embodimentsParticular reference is made now to FIG. 1, in which the referencenumeral 10 generally designates the fuse.

The ferrules 11 and 12 composed of conductive material are mounted onand close the ends of a fuse tube 13 composed of insulating material.Each ferrule has an inwardly extending annular cap for enclosing the endof the mandrel or core 15, the cap of ferrule 11 being shown at 14. Thecap 14 may be formed integrally with the remainder of the ferrule 11 andis preferably coaxially disposed therein. The sand core 15 has one end16 thereof disposed in the cap 14, and has a spiral wound fuse element17 disposed thereon, with the end of the fuse element 17 being solderedat 18 to the cap 14. The generally cylindrical space 19 between theouter wall of the sand core 15 and the inner Wall of the fuse 13 isfilled with sand especially selected for its arc quenching action andfor its porosity to provide some space for temporarily storing the gasproduced by an arc when the fuse element 17 is melted in response to anovercurrent condition therein and the electrical circuit interrupted.

The manner of attaching the end of the mandrel or core .15 to theferrule 11 does not constitute part of the instant invention. The core15 may be attached to the ferrule by utilizing the exterior surface ofthe core as shown in FIG. 1, which is the preferable method, or the core15 could, if desired, be attached to the ferrule by drilling into thecore or forming the core with a central bore in the end thereof, andutilizing a bolt, pin or stud, mounted in the ferrule and extending intothe end of the core or mandrel, somewhat similar to the mountingarrangement shown, for example, in Patent No. 2,523,139, for Fuse issuedSept. 19, 1950 to J. B. Owens, and assigned to the assignee of theinstant invention.

Particular reference is made now to FIG. 2, which shows the core 15 andfusible element 17 in somewhat greater detail. The fusible element 17 isseen to be wound on the core with sufficient spacing between turns toprovide electrical insulation, and also to provide some mechanicalstrength if desired and support for the core. The spacing between turnsof the embodiment of FIG. 2 may vary according to the method ofconstruction used.

In binding the porous sand of the core or mandrel together, I have foundthat an epoxy resin makes a suitable binder material. A suitable epoxyresin is one of the Bisphenol-epichlorohydrin type; an example of thisis one known in the trade as Shell Epon 828. The epoxy resin is mixedthoroughly with the sand to assure a firm mandrel or core when cured.The amount of epoxy resin is regulated closely to assure that theporosity or density of the mandrel or core is not reduced. Asatisfactory proportion between sand and epoxy resin is 200 parts byweight of sand to 1 part by weight of epoxy resin.

After the sand with the added epoxy resin binder which may include anadded catalyst is placed in the mandrel or core mold, it is baked tocure the resin binder. The manufacturers recommended time andtemperature may be followed. A suitable temperature is C. and a suitabletime is 2 hours for the epoxy resin mentioned here inbefore.

If desired, the cure time, as well as the shelf life of the epoxy-sandmixture can be varied by using a selected type of catalyst with theepoxy. Suitable types of catalysts are: diethylene triamine andtriethylene tetramine.

A core or mandrel so constructed according to the above teachings issulficiently rigid so that the fuse element may be tightly wound thereonin a manner which will hold the turns thereof properly spaced; at thesame time the sand of the core is so loosely bound by the epoxy resinthat energy generated by the are when the fuse blows loosens and freesthe sand of the core, so that the space .2 within the sand of the corebecomes available for gas storage, and the sand of the core assists theother sand in the fuse tube in extinguishing the arc.

Particular reference is made now to FIG. 3, where a core 25 as seen incross-section is generally cruciform, and as seen in perspectivecomprises four generally rectangular support portions disposed at spacedangular intervals of 90 around the longitudinal axis of the core withflat support surfaces extending generally parallel to the longitudinalaxis of the core, supporting surfaces 26, 27, 28 and 29 having the turnsof a fuse element 30 wound thereon.

Particular reference is made now to FIG. 4. The core or mandrel 45 isseen to be generally spiral in shape, with alternate ridge portions 46and alternate trough portions 47, and a spiral fuse element 48.

By way of further summary, in constructing my fuse I make the core ormandrel out of sand by placing a mixture of sand and a suitable bindermaterial or bonding agent aforedescribed with or without a catalyst in amold, and then baking the mixture to eliminate volatile material. Thismethod is suitable for constructing cores according to the embodimentsof FIGS. 2, 3 and 4.

The drawings and the aforegoing written description are exemplary andillustrative only and are not to be interpreted in a limiting sense.

I claim as my invention:

1. A fuse comprising, in combination, a normally rigid breakable porouscore composed of sand and a binder material, ferrules disposed at theends of the core respectivcly, a fuse element wound on the sand core andmaking electrical connection with the ferrules at both ends thereof, afuse tube composed of nonconductive material enclosing the core and thespace thereabout, and additional sand filling the space between theinner Wall of the fuse tube and the core, the sand of the core beingfreed and loosened by energy generated by the arc when the fuse blows,the sand within the fuse tube and the freed sand of the core assistingin quenching the are created when the fuse element is melted and theelectrical circuit therethrough broken, the freed sand of the core andthe sand Within the fuse tube both providing space for temporarilystoring gases generated by the are when the circuit is interrupted.

2. A fuse according to claim 1 in which the core is additionallycharacterized as being generally cylindrical in shape.

3. A fuse according to claim 1 in which the core is characterized asbeing substantially cruciform in cross section.

4. A fuse according to claim 1 in which the core maintains the turns ofthe fuse element in predetermined spaced relationship with respect toeach other until the fuse blows.

5. A fuse according to claim 1 in which the binder material includes anepoxy resin.

6. A fuse according to claim 5 in which the epoxy resin is of thebisphenol-epichlorohydrin type.

7. A fuse according to claim 5 in Which the sand and epoxy resin areproportioned substantially 200 parts by weight of sand to 1 part byweight of epoxy resin.

8. A fuse according to claim 5 including in addition a catalyst added tothe epoxy resin to control the cure time.

9. A fuse according to claim 8 in which the catalyst is diethylenetriamine.

10. A fuse according to claim 8 in which the catalyst is triethylenetetramine.

References Cited UNITED STATES PATENTS 1,545,550 7/1925 Coates 200-2,157,907 5/1939 Lohausen 200120 2,315,320 3/1943 Earle 2001 152,768,264 10/1956 Jones et al. 200-444 2,917,605 12/1959 Fahnoe 200-1142,961,514 11/ 1960 Lindell 200-120 3,166,656 1/1965 Hollmann et al200120 3,196,521 7/1965 Hollmann et a1. 29155.5

FOREIGN PATENTS 20,483 7/1903 Great Britain. 577,805 5/ 1946 GreatBritain.

BERNARD A. GILHEANY, Primary Examiner.

H. B. GILSON, Assistant Examiner.

